It is known that application of certain stresses to the crystalline lattice in the channel region of a FinFET device can reduce gate delay and increase switching speed. It is also known that for N-channel (NMOS) FinFETs and P-channel (PMOS) FinFETs, the respective relation between the direction of the stresses and the resulting change in performance, i.e., improvement or degradation, can be mutually opposite. For example, in an NMOS FinFET, tensile stress along the channel direction (i.e., the extending direction of the fin), can increase electron mobility, hence, improve the FinFET speed. However, in a PMOS FinFET the opposite can hold true in, namely, tensile stress can degrade performance while compressive stress increases electron mobility.
Conventional stressor element techniques can therefore include NMOS FinFET stressors and PMOS FinFET stressors, having substantial mutual differences in structure and materials, so as to induce respectively opposite stresses. The differences in structure and materials can add costs to the fabrication process.